
The \(n\) th term in the above sequence equals to factorial of \(n\)  that represents the number of permutations for \(n\)  elements. The (\(n\) , \(k\) )th unsigned Stirling numbers of the first kind represents the number of permutations for \(n\)  elements with \(k\)  disjoint cyclic permutations. Then, sum of the (\(n\) , \(k\) )th unsigned Stirling number of the first kind from \(k=0\)  to \(n\)  equals to the \(n\) th factorial [1]} (Fig. REF (a)).
